1251. Multi-scale X-ray techniques for assessing recycled concrete aggregate : from XRPD analysis of leftover cement in recycled aggregates to micro-CT imaging of concrete microstructureA. Bisciotti, Lucia Mancini, Alberto Viani, Vesna Zalar Serjun, Ana Mladenovič, Giuseppe Cruciani, 2025, original scientific article Abstract: The content of leftover cement paste is a crucial parameter for determining recycled aggregates quality. Various methods assess this, including wet techniques (acid dissolution, chemical degradation, water absorption), physical approaches (freeze-thaw cycles, mechanical shredding, oven-dried density, thermal disaggregation), and spectroscopic or microscopy analyses. However, these methods often lack accuracy, are time-consuming, or depend on operator skill. A novel X-ray Powder Diffraction and Rietveld quantitative phase analysis approach is introduced to improve measurements precision. Results are compared with multi-scale analyses (microscopy, Xray computed tomography, mechanical testing) on recycled aggregate concrete specimens. Findings highlight a strong correlation between leftover cement paste content and key concrete properties, including microstructure, hydration products, and mechanical performance. This study confirms that leftover cement paste content is a decisive factor in recycled concrete aggregate properties, and that the proposed method offers a rapid and reliable approach to control this parameter.
Keywords: recycled concrete aggregate, leftover cement paste, CDW, X-ray diffraction, microstructure
Published in DiRROS: 27.08.2025; Views: 347; Downloads: 222
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1252. Investigation of the interactions and electromagnetic shielding properties of graphene oxide/platinum nanoparticle composites prepared under low-dose gamma irradiationDejan Kepić, Miloš Milović, Dušan Sredojević, Andjela Stefanović, Brankica Gajić, James L. Mead, Blaž Nardin, Blaž Likozar, Janvit Teržan, Muhammad Yasir, Warda Saeed, Svetlana P. Jovanović, 2025, original scientific article Published in DiRROS: 27.08.2025; Views: 256; Downloads: 146
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1255. Coordination chemistry of copper and nickel with xenon difluoride and the hexafluororuthenate(V) anion : synthesis and structural studiesTomaž Mržljak, Evgeny A. Goreshnik, Gašper Tavčar, Melita Tramšek, 2025, original scientific article Abstract: In the photochemical reactions between MF2 (M = Cu, Ni), Ru, and F2 in anhydrous HF, Cu(RuF6)2, and Ni(RuF6)2 are formed. Only crystals of Cu(RuF6)2 are obtained during the crystallization of the powdered products. Cu(RuF6)2 crystallizes in the triclinic space group Pmathematical equation. The Cu atoms are coordinated by six F atoms, which are shared with octahedral RuF6 units. Together, they form slabs that are interconnected by van der Waals forces. In the reactions between M(RuF6)2 (M = Cu, Ni) and 2XeF2 (1:2 molar ratio), [Cu(XeF2)2](RuF6)2 and [Ni(XeF2)2](RuF6)2 are formed. They both crystallize in the monoclinic space group P21/c. The metal center is coordinated by six F atoms. Two F atoms are provided by two nonbridging XeF2 molecules, while the remaining four originate from four bridging [RuF6]- anions. In the reactions between M(RuF6)2 (M = Cu, Ni) and an excess of XeF2, [Cu(XeF2)6](RuF6)2 and [Ni(XeF2)6](RuF6)2 are formed. They are not isostructural, as the first crystallizes in the triclinic space group Pmathematical equation, while the second crystallizes in the trigonal space group Rmathematical equation. In both cases, homoleptic cations [M(XeF2)6]2+ are present, with the metal center coordinated by six nonbridging XeF2 molecules, while the [RuF6]- anions are discrete.
Keywords: coordination chemistry, X-ray diffraction, xenon difluoride
Published in DiRROS: 26.08.2025; Views: 350; Downloads: 175
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